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# The Diameter of a Wheel of a Bus is 90 Cm Which Makes 315 Revolutions per Minute. Determine Its Speed in Kilometres per Hour. [Use π = 22/7] - Mathematics

Course
ConceptIntroduction of Mensuration

#### Question

The diameter of a wheel of a bus is 90 cm which makes 315 revolutions per minute. Determine its speed in kilometres per hour. [Use π = 22/7]

#### Solution

It is given that the diameter of the wheel is 90 cm.
∴ Radius of the circular wheel, r $= \frac{90}{2} = 45 cm .$
∴ Perimeter of the wheel $= 2 \times \pi \times r = 2 \times \frac{22}{7} \times 45 = 282 . 857 cm$
It means the wheel travels 282 . 857 cm in a revolution.
Now, it makes 315 revolutions per minute.
∴ Distance travelled by the wheel in one minute $= 315 \times 282 . 857 = 89100 cm$
∴ Speed = 89100 cm per minute $= \frac{89100 cm}{1 \text{ minute }}$
Now, we need to convert it into kilometers per hour.
$\therefore \frac{89100 cm}{1\text{ minute }} = \frac{89100 \times \frac{1}{100000}\text{ kilometer }}{\frac{1}{60}\text{ hour }}$
$= \frac{89100}{100000} \times \frac{60}{1} \times \frac{\text{ kilometer }}{\text{ hour }}$
= 53 . 46 kilometers per hour

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#### APPEARS IN

RD Sharma Solution for Mathematics for Class 8 by R D Sharma (2019-2020 Session) (2017 to Current)
Chapter 20: Mensuration - I (Area of a Trapezium and a Polygon)
Ex. 20.1 | Q: 7 | Page no. 14
Solution The Diameter of a Wheel of a Bus is 90 Cm Which Makes 315 Revolutions per Minute. Determine Its Speed in Kilometres per Hour. [Use π = 22/7] Concept: Introduction of Mensuration.
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